This invention relates to a fiber reinforced structural material. More specifically, this invention relates to a composite structure comprised of high strength silicon nitride whiskers in a glass matrix.
Fiber reinforced organic matrix composites are widely used and accepted as structural materials because of their desirable attributes of high strength high modulii and low density. In general, most of these composites comprise an organic polymer matrix, such as an epoxy resin, a polyimide, a polycarbonate, or similar material. The matrices are reinforced with a wide variety of fibers including glass, carbon, graphite and boron. However, even the best of these composites are limited to an operational temperature below about 600.degree. F. (300.degree. C.).
The severe environment encountered by advanced missile systems precludes the use of organic matrices. Radomes for such systems must have acceptable resistance to rain and particle erosion as well as high thermal stability and thermal shock resistance. Generally, ceramic materials meet one or more of these requirements. One further requirement for radomes, that being transparency to X band radiation, precludes the use of certain ceramic materials. Silicon carbide yarn reinforced glass and glass ceramic composites, although very strong, tough, and environmentally stable, have been found to be essentially opaque to X band radiation. Other materials, such as boron nitride reinforced glass and glass ceramic composites, are X band transparent, but are extremely weak and brittle.
Thus, what is desired is a composite material which exhibits superior strength and toughness, high thermal stability and is transparent to X band radiation.
Accordingly, it is an object of the present invention to provide an improved silicon nitride whisker, glass matrix composite material.
Another object of the present invention is to provide a process for making an improved silicon nitride whisker glass matrix composite material.
Other objects and advantages of the present invention will become apprent to those skilled in the art from a reading of the following detailed disclosure.